1. Field of the Invention
This invention generally relates to integrated circuit (IC) fabrication and, more particularly, to a direct current (dc), type IV substrate electroluminescent device and corresponding fabrication processes.
2. Description of the Related Art
The generation of light from semiconductor devices is possible, regardless of whether the semiconductor material forms a direct or indirect bandgap. High field reverse biased p-n junctions create large hot carrier populations that recombine with the release of photons. For silicon devices, the light generation efficiency is known to be poor and the photon energy is predominantly around 2 eV. The conversion of electrical energy to optical photonic energy is called electroluminescence (EL). Efficient EL devices have been made that can operate with small electrical signals, at room temperature. However, these devices are fabricated on materials that are typically not compatible with silicon, for example type III–V materials such as InGaN, AlGaAs, GaAsP, GaN, and GaP. An EL device built on one of these substrates can efficiently emit light in a narrow bandwidth within the visible region, depending on the specific material used. Additionally, type II–VI materials such as ZnSe have been used. Other type II–VI materials such as ZnS and ZnO are known to exhibit electroluminescence under ac bias conditions. These devices can be deposited onto silicon for use in light generating devices if special (non-conventional) CMOS processes are performed. Other classes of light emitting devices are organic light emitting diodes (OLEDs), nanocrystalline silicon (nc-Si), and polymer LEDs.
A simple and efficient light-emitting device compatible with silicon, and powered by a dc voltage would be desirable in applications where photonic devices (light emitting and light detecting) are necessary. Efficient silicon substrate EL devices would enable a faster and more reliable means of signal coupling, as compared with conventional metallization processes. Further, for intra-chip connections on large system-on-chip type of devices, the routing of signals by optical means is also desirable. For inter-chip communications, waveguides or direct optical coupling between separate silicon pieces would enable packaging without electrical contacts between chips. For miniature displays, a method to generate small point sources of visible light would enable simple, inexpensive displays to be formed.
Therefore, it would be advantageous if a simple EL device could be fabricated on a Si substrate.
It would be advantageous if a Si substrate EL device could be operated with a small, dc voltage.
It would be advantageous if a Si substrate EL device could emit shorter wavelengths of light, in the blue and near-ultraviolet regions of the spectrum.